Predicting Maximum Eccentric Ground Reaction Force In Healthy Pediatric And Adolescent Athletes

PURPOSE: To assess the effects of demographic variables and strength performance on eccentric ground reaction force during jumping. METHODS: 30 healthy pediatric athletes, 11 (+/- 3.1) years, performed a series of physical performance measures. These included isometric hip abduction and adduction strength at 0 and 45 hip flexion, eccentric hamstring strength, isometric knee extension, isokinetic knee extension, 6 rep max leg-press test, countermovement jump force production and vertical jump height. Composite scores for all physical performance measures were developed by averaging the trials of each limb. Age, height, weight, sex, and participating sports were recorded. For statistical analysis, univariable linear regressions were utilized to assess the relationship between maximum eccentric ground reaction force (MEGRF) and demographic variables and physical performance measures. RESULTS: Age, height and weight were found to be independent predictors for MEGRF (p = <.05). Weight demonstrated a large effect size (r2 = .588). Sport and sex were not independent predictors of performance on MEGRF (p= > .05). Isokinetic at 60, hip abduction and adduction at 45, hip abduction at 0 degrees, and countermovement jump height were all predictive of MEGRF (p = <.05). CONCLUSIONS: MEGRF is predicted by both demographic variables and physical performance measures. The large effect of an athlete’s weight on MEGRF allows for the establishment of predictive values (figure 1). Similarly, assessing hip strength and knee extension isokinetic peak force can assist in predicting MEGRF. Therefore, benchmarking pediatric athlete strength performance and demographic factors against MEGRF will enable future investigations to establish potential risk factors for injuries that are associated with landing forces i.e. ACL ruptures, as well as assisting in return to sport decision-making.